1. Field of the Invention
The present invention relates to a fuel cell stack, specifically a fuel cell stack having a structure to discharge supplied water.
2. Description of the Related Art
In a conventional fuel cell that uses a polymer electrolyte membrane, a fuel chamber and an oxygen chamber sandwich the electrolyte membrane from opposite sides. A fuel gas in the fuel chamber is ionized through a fuel electrode, or an oxidizing gas (mainly oxygen in air) in the oxygen chamber is ionized through an oxygen electrode, and the ions are drawn through the electrolyte membrane to obtain electric power.
As shown in Japanese Patent Application Publication No. JP-A-2004-031175 (reference numerals 95, 951 in FIG. 4), after electric power is obtained, the oxidizing gas is discharged from the oxygen chamber to an exhaust chamber. Also, when the oxidizing gas flows into the oxygen chamber, coolant water is injected into the oxygen chamber from a water tank. Because the coolant water is injected into the oxygen chamber in this manner, the injected water arrives in the exhaust chamber through the oxygen chamber. The coolant water also functions to maintain the electrolyte membrane in a moist state. To maintain all of the electrolyte membranes that make up a fuel cell stack in a moist state, the oxygen and the water must be supplied uniformly to each of the stacked electrolyte membranes.
However, when the coolant water that is supplied to the oxygen chamber drops from an air flow passage 95, a water droplet forms at an opening 951, then falls after growing to a size that can drip. There is concern that a water droplet that accumulates at the opening 951 might obstruct air flow in the air flow passage 95, thereby reducing the cooling action.